I would rather see the Prebles station at a crossing on the line somewhere (in a semi-public place, like Trask's crossing) rather than repurposed into an electrical shed.
For the electrical shed, I like Start's idea for a boxcar-like body; from the outside it could look like a Portland Co. car, but built with all modern construction materials, set on a concrete pad, etc. I also like Dave C's idea to model it after a car like 61, 301, 302, or 303; all which had end doors and windows. (See Narrow Gauge in the Sheepscot Valley, Vol. IV, pgs 58, 64 - 70)